JavaScript: Find a pair of elements from an specified array whose sum equals a specific target number

JavaScript Array: Exercise-26 with Solution

Write a JavaScript program to find a pair of elements (indices of the two numbers) in a given array whose sum equals a specific target number.

Input: numbers= [10,20,10,40,50,60,70], target=50
Output: 2, 3

Visual Presentation:

Sample Solution:

JavaScript Code:

// Function to find two indices in the array 'nums' whose elements sum to the 'target_num'
function twoSum(nums, target_num) {
  // Initialize an empty array 'map' to store the difference between 'target_num' and elements in 'nums'
  var map = [];
  // Initialize an empty array 'indexnum' to store the indices of the two numbers
  var indexnum = [];
  
  // Iterate through each element in the 'nums' array
  for (var x = 0; x < nums.length; x++) {
    // Check if the current element's complement exists in the 'map' array
    if (map[nums[x]] != null) {
      // If found, store the indices of the two numbers and break out of the loop
      var index = map[nums[x]];
      indexnum[0] = index;
      indexnum[1] = x;
      break;
    } else {
      // If not found, store the index of the current element's complement in the 'map' array
      map[target_num - nums[x]] = x;
    }
  }
  
  // Return the array containing the indices of the two numbers
  return indexnum;
}

// Output the result of the twoSum function with a sample array and target number
console.log(twoSum([10,20,10,40,50,60,70], 50));

Output:

[2,3]

Flowchart:

ES6 Version:

// Function to find two indices in the array 'nums' whose elements sum to the 'target_num'
const twoSum = (nums, target_num) => {
  // Initialize an empty array 'map' to store the difference between 'target_num' and elements in 'nums'
  const map = [];
  // Initialize an empty array 'indexnum' to store the indices of the two numbers
  const indexnum = [];

  // Iterate through each element in the 'nums' array
  for (let x = 0; x < nums.length; x++) {
    // Check if the current element's complement exists in the 'map' array
    if (map[nums[x]] != null) {
      // If found, store the indices of the two numbers and break out of the loop
      const index = map[nums[x]];
      indexnum[0] = index;
      indexnum[1] = x;
      break;
    } else {
      // If not found, store the index of the current element's complement in the 'map' array
      map[target_num - nums[x]] = x;
    }
  }

  // Return the array containing the indices of the two numbers
  return indexnum;
};

// Output the result of the twoSum function with a sample array and target number
console.log(twoSum([10, 20, 10, 40, 50, 60, 70], 50));

Live Demo:

See the Pen JavaScript - Find a pair of elements from an specified array whose sum equals a specific target number - array-ex- 26 by w3resource (@w3resource) on CodePen.

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